Success in plant husbandry is measured by the quantity and quality of the desired crop which is produced, whether the crop is seed or grain such as corn, wheat or soybeans; fruit such as grapes, apples, oranges or tomatoes; or other parts of the plant such as tubers (potatoes, for example) or leaves (lettuce, for example).
Quality is measured with respect to various desired characteristics of the particular crop such as moisture content, acidity or alkalinity, shape, color, taste, etc. Quality depends on many factors which, outside of special and expensive artificial environments such as hydroponic farming in greenhouses, are difficult to control. In a field, the chemical and physical makeup of the soil may be altered by application of fertilizers, chemicals, crop rotation and different methods of cultivation. The timing and extent of rainfall, if inadequate, may be supplemented by spraying or irrigation systems.
Soil and air temperatures are largely uncontrollable outside of artificial enclosures. Efforts usually must be made to control weeds and insects which interfere with plant growth.
Quality and quantity are sometimes antithetical goals. For example, a prize winning tomato weighing several pounds might not be very tasty. However, in general, larger quantities of crop yield are desirable if the input in the cost and labor of producing a larger crop is less than the financial return from the increase in the crop yield.
Crop yield is measured in various ways for different types of crops. For most varieties of Zea mays L., commonly referred to as corn, which is grown in the United States, yield is measured in bushels produced per acre of planted land. The term "bushel" may have more than one meaning. According to the American College Dictionary, the term may mean a unit of dry measure, which is to say "volume", equal to 2,150.42 cubic inches in the United States. In Great Britain, the Imperial bushel is equal to 2,219.36 cubic inches. A "bushel" may also be a unit of weight equal to the weight of a volume based bushel of a given commodity.
The term "bushel", as used herein to explain crop yield, means 56 pounds of shelled (removed from the corn cob) corn having 15.0% moisture and 2.0% foreign material (husks, cob pieces, dirt, other grains, etc.). This is the standard for "No. 2 Yellow Corn" as defined by the Federal Grain Inspection Service. It is the standard used in the purchase of grain from the farmer by elevators, in sales by elevators to users or traders, and in trading on the commodities and futures markets. It is also the standard used in agronomic research to measure results of experiments.
Since it would be coincidence for almost any load of shelled corn to exactly match the standard in all respects, in measuring yield the gross weight of the shelled corn is adjusted for deviations from the standard. In addition, shelled corn may be dried, particularly if storage is contemplated, thus reducing its gross weight but also reducing any downward adjustment of the dried weight to measure the adjusted weight and the yield.
Corn intended for direct human consumption usually called "sweet corn" , in commercial sales is measured by the ton and includes the corn cobs. Thus, this is also a measure by weight, rather than by volume or number of ears. Such a measure is roughly comparable to the standard bushel measurement described above. In agronomic studies of corn yield, even for sweet corn, the No. 2 Yellow Corn standard is used because it is more precise. The present planting arrangement and method is applicable to sweet corn as well as for corn not intended for direct human consumption.
Thus, as set forth in this application and in the claims, "yield" means the number of bushels of shelled corn adjusted to the No. 2 Yellow Corn standard produced per acre of planted farmland.
The term "corn" is also an ambiguous term. Broadly, it can refer to any edible grain such as wheat in England and barley in Scotland. Generally in the United States and other parts of the Western hemisphere, it refers to a member of the maize family, which was cultivated, bred and improved by natives of the Western hemisphere and has been, over the last century or more, extensively bred and hybridized for greater usefulness to mankind. As used herein the term corn refers only to a variety of Zea mays L.
Even within this group there are great variations in a number of characteristics. One of these is the full grown height of the corn plant. For example, there is bantam corn which typically grows to about four feet in height and varieties grown in Central America which mature with a height of about twelve feet.
Applicant's experiments utilized several varieties of corn widely used in the Midwestern part of the United States which normally attain a full grown height, on average, of 8.5 feet or 102 inches. Of course, the eventual height of individual plants will vary depending on growing conditions. Unless otherwise indicated by the context in this application, "height" means normal full grown height attained by a corn plant of any variety.
All crops are produced as a result of photosynthesis, the conversion of energy in the form of light to plant material. Simplistically, it could be hypothesized that if more light were applied to plants, they would grow more and produce greater yields. U.S. Pat. Nos. 3,324,593 and 3,931,695 are examples of expensive enclosed and controlled environment systems that supply artificial light to plants to supplement natural light.
Applicant's invention uses only natural light in an unenclosed environment.
Working only in an unenclosed environment, others have proposed alternating rows of short plants and tall plants so that increased light reaches the higher leaves of the tall plants to increase the rate of their photosynthetic processes. See Kulivdze, SU 1664182 and SU 1664183 for grapevines. Somewhat analogously, U.S. Pat. No. 4,327,521 suggests for hedgerow type plants such as tea, trimming one side of the plants in each row at an angle, which maximizes exposure to natural light, and harvesting the tea leaves by a cutter at the same angle.
In connection with corn (Zea mays L.) which is a tall plant usually over six feet high at maturity, some academic studies have researched the effects of light on crop yield. In a study by Pendleton et al., reported in 59 Agronomy Journal 395 (1967) and in a study by Winter et al., reported in 62 Agronomy Journal 181 (1970), there are reports of experiments using large reflectors placed near corn plants throughout the growing season to increase the amount of natural light incident on the plants. Ottman et al. reported experiments in 80 Agronomy Journal 619 (1980) in which fluorescent lights placed within the corn canopy increased yields. As might be expected, in an experiment by Early et al., reported in 7 Crop Sciences 151 (1966), shaded corn plants had lower yields.
The reflectors and fluorescent lights used by Pendleton, Winter and Ottman, while necessary to developing their scientific conclusions, do not provide practical, useful or economic means to increase yields. Such apparatus within an open commercial crop field will interfere with or prevent cultivation and application of herbicides and pesticides and will always have to be removed before harvesting to permit the entry of harvesting equipment.
Traditionally, corn and other crops have been planted in rows spaced between 30 inches apart and 36 inches apart, all equally spaced. Such spacing originally arose because of the space required for a horse to pull equipment through a field for planting, cultivation and harvesting. The same spacing continued when horses were replaced by tractors. More recently, there has been a widely accepted trend to plant corn in more narrowly spaced rows. This provides more corn plants in a field of a given size. Since each plant generally produces one ear of corn, it has been felt that with more plants, there will be more ears and hence a higher yield.
As will be seen below, this invention provides a teaching which is directly contrary to the presently accepted approach and even the traditional approach to row spacing. However, the invention does not merely involve wider spacing of rows. Because of the wide variation in the full growth height of corn plants, the invention is defined in terms of the ratio of eventual plant height to row spacing, rather than in terms of specific row spacing measurements.
The invention also makes more practical the use of "inter-cropping". The planting of two or more crops in the same field which can increase the economic return on a particular field.